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<h2 class="chapter" id="Other-Directives-1"><span>8 Other Directives<a class="copiable-link" href="#Other-Directives-1"> &para;</a></span></h2>

<a class="index-entry-id" id="index-_0023ident"></a>
<a class="index-entry-id" id="index-_0023sccs"></a>
<p>The &lsquo;<samp class="samp">#ident</samp>&rsquo; directive takes one argument, a string constant.  On
some systems, that string constant is copied into a special segment of
the object file.  On other systems, the directive is ignored.  The
&lsquo;<samp class="samp">#sccs</samp>&rsquo; directive is a synonym for &lsquo;<samp class="samp">#ident</samp>&rsquo;.
</p>
<p>These directives are not part of the C standard, but they are not
official GNU extensions either.  What historical information we have
been able to find, suggests they originated with System V.
</p>
<a class="index-entry-id" id="index-null-directive"></a>
<p>The <em class="dfn">null directive</em> consists of a &lsquo;<samp class="samp">#</samp>&rsquo; followed by a newline,
with only whitespace (including comments) in between.  A null directive
is understood as a preprocessing directive but has no effect on the
preprocessor output.  The primary significance of the existence of the
null directive is that an input line consisting of just a &lsquo;<samp class="samp">#</samp>&rsquo; will
produce no output, rather than a line of output containing just a
&lsquo;<samp class="samp">#</samp>&rsquo;.  Supposedly some old C programs contain such lines.
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